Create terrazzo material/pattern with the standard textures
Just switch a Voronoi texture to Cells coloring, and drive it through a Color Ramp node set to Constant interpolation mode.

Adjust the Color Ramp stops to the desired color ratio so that the amount of colored flakes is close to the reference image.

You would generally want narrow black, orange and green strips, over a broader white background, so adjust proportions accordingly.

Speckle size can be adjusted from texture scale parameter. Changing size may also require adjusting color stop positions.